This invention relates to a drip-proof connector widely used in connection between electric cables or the like and electric and electronic appliances such as cameras for televisions, servomotors for machine tools and the like, and more particularly to an insert for a drip-proof connector.
A drip-proof connector is generally constructed by a cylindrical shell 1 made of a metal or a plastic material, an insert 2 made of an insulating elastic substance such as rubber or the like and arranged in the shell 1, and at least one contact 3 piercing through the insert 2 as shown in FIG. 1.
With the above drip-proof connector, the insert 2 is made of a material having a repulsive elasticity, for example, rubber, and an outer diameter of the insert 2 is larger than an inner diameter of the shell 1 and a diameter of a contact piercing aperture of the insert is smaller than an outer diameter of the contact so that air-tightness between the shell 1 and the insert 2 and between the contact 3 and the insert 2 is accomplished to ensure a water-proof property to a certain extent. If it is required to improve the air-tightness and water-proof property of the connector, projections 15 are provided on inside of the shell 1 or the contact 3 is provided with an enlarged portion 31 which is often coated with an adhesive. Such projections 15 and the enlarged portion 31 serve to prevent the insert 2 and the contact 3 in the shell 1 from moving relatively to the shell in its axial direction.
The drip-proof connector of the prior art above described fulfills requirements on the air-tightness and water-proof property to a certain extent. However, they are not necessarily enough and complete. Further, such a drip-proof connector of the prior art involves the following disadvantages.
(1) In most cases, contacts 3 more than five are inserted into the insert 2 of the connector. With such a plurality of contacts being inserted in the insert 2, the compressive force does not act uniforming upon surfaces of the insert 2. Such an uneven distribution of the compressive force naturally causes excess and deficiency in compressive force in places, particularly between the shell 1 and the insert 2 and between the insert 2 and the contacts 3. Therefore, water would enter through the places where the compressive force is not enough. PA0 (2) In assembling the connector, the insert 2 is once compressed to an outer diameter smaller than an inner diameter of the shell 1 and then inserted into the shell 1. In order to remove the insert 2 from the shell 1 for some reason after assembled, therefore, a special tool is needed for the removal of the insert. Even if such a special tool is used, there is a tendency for the insert 2 to be damaged in removing it from the shell 1. PA0 (3) The compressive force acting between the insert 2 and the shell 1 is regulated by an elasticity of the insert material. Therefore, no air-tightness (drip-proof effect) in excess of the regulation resulting from the insert material is any longer obtained. PA0 (4) In order to obtain the air-tightness between the insert 2 and the shell 1, the pressure to be applied to the insert is fairly high. Accordingly, assembling and disassembling of the connector could not be effected in simple and easy manner. Particularly, in working sites not having sufficient tools and implements, the assembling of the connector is very difficult, if not impossible.